1. Field of the Invention
The invention relates to the use of special yarns for manufacturing stiff cords, stiff cords made of special yarns, and V-belts containing stiff cords made of special yarn.
2. Description of Related Art
In manufacturing V-belts, especially V-belts with open flanks, so-called stiff cords are used which serve to reinforce the V-belts. As a rule, V-belts with open flanks have trapezoidal cross sections. They can also have a cross section composed of a plurality of trapezoids superimposed on one another. Cross sections of this kind are described for example in the informational publication from Akzo nv entitled "Akzo Industrial Yarns for Transmission Belts IER/148," 8, 1991. To make the V-belts, the stiff cords are embedded in an elastomer in such fashion that a wide elastomer strip results which contains the stiff cords as reinforcing inserts to reinforce it. The V-belts are cut from this strip, with the final cross sectional shape of the V-belts being obtained by cutting. To be able to ensure clean cuts, in the type of manufacture of V-belts known at the present time, assurance must be provided that the stiff cords, composed of a plurality of filaments, do not fray or separate. Resistance to fraying or separating of the stiff cords has been achieved by methods known previously by subjecting the cords to a dip treatment before embedding them in the elastomer, with a resin, based as a rule on a diisocyanate prepolymer, dissolved in toluene, methylene chloride, or methyl chloroform, being used as the dip bath liquid. This dip bath was followed by drying the dipped cords. The evaporation of the above-mentioned solvents required for drying poses a serious problem. Firstly, toxic and highly explosive vapors are produced when these solvents are evaporated; secondly, these solvents are very expensive, so that the solvent vapors must be drawn off as completely as possible in a costly process, and must be recovered as completely as possible in liquid form. The dipped and dried cords are called stiff cords.